Title: Optical and Ultraviolet Observations of the Narrow-Lined Type Ia SN 2012fr in NGC 1365 Show Chinese title

Title: NGC 1365中窄线型Ia型超新星SN 2012fr的光学和紫外观测

Abstract: Extensive optical and ultraviolet (UV) observations of the type Ia supernova (SN Ia) 2012fr are presented in this paper. It has a relatively high luminosity, with an absolute $B$-band peak magnitude of about $-19.5$ mag and a smaller post-maximum decline rate than normal SNe Ia [e.g., $\Delta m _{15}$($B$) $= 0.85 \pm 0.05$ mag]. Based on the UV and optical light curves, we derived that a $^{56}$Ni mass of about 0.88 solar masses was synthesized in the explosion. The earlier spectra are characterized by noticeable high-velocity features of \ion{Si}{2} $\lambda$6355 and \ion{Ca}{2} with velocities in the range of $\sim22,000$--$25,000$ km s$^{-1}$. At around the maximum light, these spectral features are dominated by the photospheric components which are noticeably narrower than normal SNe Ia. The post-maximum velocity of the photosphere remains almost constant at $\sim$12,000 km s$^{-1}$ for about one month, reminiscent of the behavior of some luminous SNe Ia like SN 1991T. We propose that SN 2012fr may represent a subset of the SN 1991T-like SNe Ia viewed in a direction with a clumpy or shell-like structure of ejecta, in terms of a significant level of polarization reported in Maund et al. (2013). Show Chinese abstract

Abstract: 本文介绍了对Ia型超新星（SN Ia）2012fr的广泛光学和紫外线（UV）观测。它的相对亮度较高，绝对$B$波段峰值约为$-19.5$星等，且最大值后的衰减率比正常SN Ia小[e.g.,$\Delta m _{15}$($B$)$= 0.85 \pm 0.05$星等]。根据紫外和光学光变曲线，我们得出爆炸中合成了约0.88太阳质量的$^{56}$Ni。 早期的光谱特征表现为显著的高速特征\ion{Si}{2} $\lambda$ 6355 和\ion{Ca}{2}，速度范围为$\sim22,000$至$25,000$公里每秒$^{-1}$。在极大亮度附近，这些光谱特征被主序成分主导，这些成分明显比正常的Ia型超新星狭窄。 光球的最大速度在大约一个月内几乎保持恒定，约为$\sim$12,000 公里每秒$^{-1}$，这类似于一些明亮的 Ia 型超新星（如 SN 1991T）的行为。 我们提出，SN 2012fr 可能代表了一类类似于 SN 1991T 的 Ia 型超新星，从具有团块状或壳状喷发结构的方向观测到，这是基于 Maund 等人（2013）报告的显著偏振水平。